<!DOCTYPE html>
<html>
<head>
	<title></title>
</head>
<body>

<ul id='ul1'>
	<li></li>
	<li></li>
	<li class='box'></li>
	<li></li>
	<li></li>
	<li></li>
	<li></li>
</ul>
<script type="text/javascript">
	function getByClass(oParent, sClass){
		var aEle=oParent.getElementsByTagName('*')
		var aResult = []
		var i=0

		for(i=0;i<aEle.length;i++){
			if(aEle[i].className=sClass){
				aResult.push(aEle[i])
			}
		}
		return aResult
	}

	window.onload=function(){
		var oUl = document.getElementById('ul1')
		var aBox=getByClass(oUl, 'box')
		alert(aBox)

		for(i=0;i<aBox.length;i++){
			aBox[i].style.background='blue'


		}
	}
</script>

</body>
</html>